Slice potatoes thinly into a 2-quart baking dish. Add salt mixed with water. Cover and cook on HIGH for 18 minutes, stirring every 5 minutes. Drain.

To make sauce: In a 4-cup measure, micro-melt butter. Whisk in flour, adding milk gradually. Cook on HIGH for 6 minutes, stirring every 2 minutes until mixture thickens. Add cheese, salt and garlic powder, and fold sauce into potatoes. Top with bread crumbs. Cover with waxed paper and microwave on HIGH for 7 minutes.